Laminated polyethylene foam sheets are desirable for the packaging industry for packaging delicate products as above described. Such sheets are cut, in blocks and cavities are made in the blocks to support delicate products. The polyethylene foam block is then placed in close frictional contact in a shipping carton. This type of packaging is particularly useful for shipping fragile articles in that the article is protected all about in the polyethylene foam block which has the quality of retaining its shape while permitting flexibility in assembly and providing protection to the product. However, a disadvantage with known polyethylene foam laminated sheets is that to laminate the sheets, it is the usual practice to position a bonding sheet between layers of polyethylene foam sheets. The bonding sheet is heated and provides an adhesive between opposed surfaces of polyethylene foam sheets. Known methods and machines for making these are limited in that they cannot make thick laminated sheets from a plurality of these polyethylene foam sheets due to the instability of such lamination. Also, the use of bonding intermediate sheets has not proved adequate in that these bonding sheets sometimes detach from the surfaces of opposed polyethylene sheets, particularly if they are cut in small pieces. The use of bonding plastic sheets also increases the cost of the finished product. This process of manufacture is also slow.
By using bonding plastic sheets between foam sheets it is difficult to line-up the thin bonding plastic sheet in position as it is unstable. This causes machine stoppages and increases the cost of the production. It also makes laminated sheets which are not perfectly bonded together all along their surfaces. With this process only two polyethylene foam sheets are bonded together and the laminated product is thus limited in thickness.